PREreview of Bacterial RNA promotes proteostasis through inter-tissue communication inC. elegans

This study investigates the role of bacterial RNA in promoting proteostasis in C. elegans, demonstrating that dietary RNA species derived from bacteria can reduce protein aggregation in muscle cells. It was shown that this effect is dependent on RNAi machinery and inter-organ communication between the intestine, germline, and muscle. The findings suggest that bacterial-derived RNA elicits a systemic response in C. elegans, protecting against protein aggregation through mechanisms involving autophagy, RNAi, and inter-tissue communication. While the manuscript is generally well-written, some concerns still require further attention.

Major points:

1. Although the OP50 diet results in more protein aggregates in the worms compared to the HT115 diet, it also led to a higher brood size and better fitness. The authors should elaborate on the correlation between the protein aggregate phenotype and the brood size/development phenotypes. Additionally, how do bacterial RNAs and the host RNAi machinery differentially regulate these two phenotypes?

2. The authors observed that autophagy induction protects animals from protein aggregation in body wall muscles when fed on HT115 diet compared to OP50 diet. However, autophagy was examined in hypodermal seam cells. The authors should include images of autophagosomes in body wall muscles. Also, are there more protein aggregates observed in other tissues (e.g. intestine, germline and hypodermis)? Did the authors conduct tissue-specific knockdown experiments of autophagy genes to determine if the regulation of protein aggregation by autophagy is cell-autonomous or non-autonomous?

3. The authors showed that while germline RNAi machinery is required for the protective effect against protein aggregation in the body wall muscle of HT115-fed worms, it is not sufficient on its own. Similarly, the intestine alone does not provide this protection. The authors should discuss the possible underlying regulatory mechanism. How do RNAi machineries in other tissues contribute to this process? Additionally, is the germline RNAi machinery involved in any transgenerational effects?

4. In the mixed dietary experiments, the OP50/HT115 ratios of 1:1, 1:10, and 10:1 all conferred significant protection against protein aggregates. Are there any significant differences in protein aggregation between these ratios? The authors should discuss how this is regulated by RNAi machinery activities. Is it due to the dose-dependent regulation of bacterial RNA concentration? or just a certain type of RNA could be enough to elicit protection?

Minor points:

1. Figure 3G, besides HT115-derived RNA, did the authors also test the injection of RNA derived from OP50 and OP50(xu363) to see if protein aggregation in OP50-fed worms can be rescued? Is there any difference between using OP50-derived RNA and HT115-derived RNA regarding aggregate formation in muscle cells?

2. Does the length of RNA matter in this regulation of protein aggregation?

3. Line 234: The name OP50(xu363) is not consistent in its format.

4. No comment on the supplementary figures is provided due to their absence in the biorxiv version.

Competing interests

The authors declare that they have no competing interests.